Meetings or events such as a convention, party, or wedding, will often involve a combination of many carefully timed activities. Some of the activities correspond to guests accepting an invitation, arriving at an event, leaving the event, among others. Historically, an invitation would be mailed to an invitee and the invitee would either call or mail a response. Any changes to the event details or further communication regarding the event would involve another letter or a phone call.
More recently, electronic calendar systems that are often tied to electronic mail (e-mail) have become an additional way for communicating invitations to events. Some electronic calendar systems allow an invitee to give notice of their intention to accept or decline an invitation by responding electronically, as well as to add event details to the invitees electronic calendar. Some electronic calendar systems also allow changes to the event information to be automatically communicated to invitees.